Hydroconversion catalyst and method for making the catalyst

ABSTRACT

A high-activity hydrotreating catalyst, having a low density, suitable for deep removal of sulfur, nitrogen, micro-carbon residue and organometallic contaminants from hydrocarbon feedstocks is disclosed. Further disclosed is a method of preparation of this catalyst, which may contain 0.3-10 wt % of a Group IVB metal promoter, 5-25 wt % of a Group VIB metal component, and 1-8 wt % of a Group VIII metal, along with a method of hydrotreating employing this catalyst.

FIELD OF THE INVENTION

[0001] This invention is directed to a high activity hydrotreating catalyst having low density and a method of preparing it. This invention is further concerned with processes employing this catalyst in the removal of sulfur, nitrogen, micro-carbon residue and organometallic contaminants from hydrocarbon feedstocks.

BACKGROUND OF THE INVENTION

[0002] Crude oil and heavier fractions and/or distillates derived from crude oils contain various contaminants, including sulfur, nitrogen, micro-carbon residue and organometallic compounds. Feedstocks have a wide range of contaminants level, depending on the origin of the crude oil, and the actual boiling range of the feedstock. These contaminants may poison catalysts used in the refining and upgrading of petroleum fractions, or be otherwise objectionable because combustion of fuels containing some of these contaminants releases noxious, corrosive and polluting byproduct gases. The removal of these contaminants is most commonly done by catalytic hydrotreating, where the contaminated feedstock is contacted with a supported catalyst in the presence of hydrogen, under a wide range of temperature, pressure and space velocity depending on the specifics of the refinery.

[0003] The profitability of a hydrotreating unit is highly dependent on the performance of the catalyst, mainly its activity and stability over time, and its cost. Refiners are facing increasingly stringent pressure to improve the profitability of their hydrotreating units, and have turned to catalyst suppliers to secure lower-cost and higher-performance hydrotreating catalysts. It has generally been very difficult to develop hydrotreating catalysts with improved performance at lower cost. Generally, better-performing catalysts tend to be more expensive, while lower-cost catalysts typically sacrifice some aspect of catalytic performance.

SUMMARY OF THE INVENTION

[0004] This invention is directed to the composition and preparation of a low density, high activity hydrotreating catalyst for deep removal of sulfur, nitrogen, micro-carbon residue and organometallic contaminants in petroleum feedstocks. High activity hydrotreating catalysts can operate effectively at high space velocities and relatively low temperatures. The invention is especially directed toward the preparation of a catalyst having excellent hydrotreating activity and stability for the deep removal of sulfur, nitrogen, micro-carbon residue and organometallic contaminants in feedstocks containing low to moderate levels of organometallic compounds. Alternately, the catalyst of this invention may be used in the back-end of hydrotreating units processing where heavier feedstocks containing larger levels of organometallic compounds would have been pre-hydrotreated in the front-end. Examples of feedstocks well suited for the present invention include total crude oil, atmospheric and vacuum residue, deasphalted oils, and atmospheric and vacuum gas oils.

[0005] The catalyst of the current invention provides overall better performance at a lower cost to the refiner. The catalyst cost savings are principally related to a lower catalyst density, which allows refiners to fill up reactor volume with a lower total weight of catalyst, therefore lowering the overall catalyst cost. The catalyst activity was optimized by the effective combination of pore structure and active metals, thereby resulting in a high activity, low density catalyst.

[0006] A preferred method of making the hydrotreating catalyst of this invention comprises: (a) mixing a refractory inorganic oxide carrier with at least one metal promoter from Group IVB; (b) adding an aqueous acidic solution comprising at least one component from Group VIII and at least one component from Group VIB and potentially additional acidic compounds; (c) shaping, drying and calcining the catalyst particles; and (d) post-impregnating the catalyst with additional hydrogenation components including at least one component from Group VIII metal and at least one component from Group VIB metal, drying and calcining and the use of the catalyst so prepared for deep removal of sulfur, nitrogen, micro-carbon residue and organometallic contaminants in hydrotreating service. This catalyst is most effective at the back end of hydrotreating units where exposure to organometallic contaminants is minimal, or in applications where feedstocks with lower concentration of organometallic contaminants are processed. The Group IVB metal promotes hydrodesulfurization.

DETAILED DESCRIPTION OF THE INVENTION

[0007] Catalyst

[0008] A method is described for making a catalyst wherein an aqueous acidic solution is made with at least one component from Group VIII and at least one component from Group VIB. The preferred Group VIII metal compounds used in this method include nickel and cobalt compounds. The preferred Group VIB metal compounds which may be used include molybdenum and tungsten. This aqueous acidic solution is added to a refractory inorganic oxide carrier. The carrier may have been previously mixed with at least one metal promoter from Group IVB. The Group IVB metal promoters which could be used in this method include titanium, zirconium and hafnium, with titanium compounds preferred. Alumina is the preferred inorganic oxide carrier used in the present invention, although alumina may be combined with other refractory support materials such as silica or magnesia. The mixture could be further treated by a suitable acid, including acetic acid, sulfuric acid, oxalic acid, hydrochloric acid, formic acid, nitric acid, phosphoric acid and citric acid. The catalyst particles are shaped, dried and calcined in air at temperatures from about 750° F. to 1500° F. for 30 to 180 minutes. The catalyst may be further impregnated using standard impregnating procedures with hydrogenation components from Group VIII and Group VIB. The broad ranges and preferred ranges of Group IVB metal promoter and Group VIII and Group VIB hydrogenation metal components are shown below: TABLE 1 Broad Range Preferred Range Group IVB Metal Promoter 0.3-10%  3-6% Group VIB Metal Component  5-25% 10-20% Group VIII Metal Component 1-8% 2-4%

[0009] The catalyst of this invention has a pore volume falling within a range of 0.40-0.70 cc/g, a pore size distribution peak falling within a range of 50-110 angstroms, and less than 5% macropores, defined as pores larger than 1000 angstroms. The pore size distribution is relatively narrow with at least 40% of the pore volume contained in pores with diameters falling within 20 angstroms of the peak.

[0010] Preferably, the catalyst of this invention has a pore volume falling within a range of 0.450.55 cc/g, a pore size distribution peak falling within a range of 55-90 angstrom, and less than 3.5% macropores. The pore size distribution is relatively narrow with at least 45% of the pore volume contained in pores with diameters falling within 20 angstroms of the peak, on either side.

[0011] Pore volume as described here is the volume of a liquid which is adsorbed into the pore structure of the sample at saturation vapor pressure, assuming that the adsorbed liquid has the same density as the bulk density of the liquid. The liquid used for this analysis was liquid nitrogen. The procedure for measuring pore volumes by nitrogen physisorption is further laid out in D. H. Everett and F. S. Stone, Proceedings of the Tenth Symposium of the Colstom Research Society, Bristol, England: Academic Press, March 1958, pp. 109-110.

[0012] Feeds and Conditions

[0013] The catalyst of the present invention can be used for hydrotreating feedstocks, including crude oils, unprocessed and partially hydrodemetallized vacuum and atmospheric residua, deasphalted oils, and vacuum and atmospheric gas oils. The present invention is particularly well suited for deep removal of sulfur, nitrogen, micro-carbon residue, and organometallic compounds contained in these feedstocks.

[0014] These feedstocks can be passed over the catalyst of the present invention at a liquid hourly space velocity in a reactor of about 0.05 to about 5.0, preferably from about 0.1 to about 3.0, while maintaining the reaction zone at a temperature of from 500° F. to about 850° F., preferably from about 550° F. to about 800° F., while under a total pressure of about 450 to about 3500 pounds per square inch gauge, preferably from about 600 to about 2800 pounds per square inch gauge, and a hydrogen partial pressure of from about 350 to about 3200 pounds per square inch gauge, preferably from about 500 to about 2500 pounds per square inch gauge.

EXAMPLES Example 1

[0015] A Catalyst was Prepared as Follows:

[0016] An acidic solution was prepared by adding 288 g of MoO₃ and 82 g of NiCo₃ to 600 ml of H₂O at room temperature, while mixing. 20 g of 85% H₃PO₄ was added over a two-minute period, while mixing. The solution was heated up to 185° F. over 30 minutes, and held between 185-220° F. for 1 hour. The solution was then cooled down to room temperature and diluted to a total volume of 1000 ml. This solution was labeled solution A.

[0017] 2200 g of dry alumina was charged into an Eirich mixer. 2150 ml of water and 480 ml of solution A were added, and mixed for 25 minutes, then the wet mix was extruded. The extrudates were dried overnight at 250° F., and calcined at 1100° F. for 90 minutes. Then, 245 g of finished base were post-impregnated with 64 ml of solution A mixed with 146 ml of water. The finished catalyst was calcined at 950° F. for 60 minutes.

Example 2

[0018] A Catalyst was Prepared as Follows:

[0019] Solution A was Prepared as Described in Example 1.

[0020] 1500 g of dry alumina was charged into an Eirich mixer. 1600 ml of water and 222 ml of solution A were added, and mixed for 25 minutes, then the wet mix was extruded. The extrudates were dried overnight at 250° F., and calcined at 1400° F. for 90 minutes. Then, 152 g of finished base were post-impregnated with 106 ml of solution A mixed with 50 ml of water. The finished catalyst was calcined at 950° F. for 60 minutes.

Example 3

[0021] A Catalyst was Prepared as Follows:

[0022] Solution A was Prepared as Described in Example 1.

[0023] 2200 g of dry alumina were charged into an Eirich mixer. 2150 ml of water and 480 ml of solution A were added, and mixed for 25 minutes, then the wet mix was extruded. The extrudates were dried overnight at 250° F., and calcined at 1100° F. for 90 minutes. Then, 254 g of finished base were post-impregnated with 155 ml of solution A mixed with 61 ml of water. The finished catalyst was calcined at 950° F. for 60 minutes.

Example 4

[0024] A Catalyst was Prepared as Follows:

[0025] Solution A was Prepared as Described in Example 1.

[0026] 1522 g of dry alumina were charged into an Eirich mixer, and mixed with 129.5 g of TiO₂. 2050 ml of water and 413 ml of solution A were added, and mixed for 18 minutes, then the wet mix was extruded. The extrudates were dried overnight at 250° F., and calcined at 1100° F. for 90 minutes. Then, 228 g of finished base were post-impregnated with 144 ml of solution A mixed with 29 ml of water. The finished catalyst was calcined at 950° F. for 60 minutes.

[0027] The catalysts in Examples 1, 2, 3 and 4 are contrasted with a commercial hydrotreating catalyst. The feed used in this comparison is a demetallized Arabian light atmospheric residuum, spiked with DMDS (2.45 g of DMDS/100 g of feed) to simulate the usual concentration of H₂S expected if the non-demetallized feed had been processed in-situ.

[0028] The temperatures shown in Table 2 are typical of a pre-processed atmospheric residuum feedstock. TABLE 2 Gravity, ° API 18.2 Sulfur, wt % 1.8 Nitrogen, wt % 0.2 Micro-Carbon Residue, wt % 7.4 Asphaltenes, wt % 1 Nickel, ppm 6.7 Vanadium, ppm 11.75 Distillation, vol. % - ° F. St/5 452/638 10/20 681/743

[0029] The hydrotreating conditions used in this example are listed below: TABLE 3 Total Pressure, psig 2250 Feed Rate (LHSV), 1/hr 0.525* Hydrogen/Hydrocarbon Fee Rate, scf/bbl 5000

[0030] The catalyst was loaded to a constant reactor volume target, resulting in significant differences in actual dry catalyst weight loaded, depending on the particle density of the catalyst, as shown in Table 4.

[0031] The catalysts were activated by a pre-sulfiding step before contact with the hydrocarbon feed.

[0032] The catalysts of Example 1, Example 2, Example 3, and Example 4 were compared for sulfur, nitrogen, micro-carbon residue and vanadium removal by running at a prescribed temperature plan, ranging from 700° F. at start-of-run to 730° F. at end-of-run (450 hours). The measure of catalyst performance was the normalized catalyst temperature required to meet target product properties. It is the temperature at which a catalyst must operate in order to remove certain amounts of sulfur, nitrogen, micro-carbon residue or vanadium from the feedstocks. The lower this temperature, the more active the catalyst.

[0033] The normalized temperature is related to the distillation of the feedstock since lighter feedstocks contain fewer contaminants and are easier to process (normalized temperatures are lower) while heavier feedstocks (such as vacuum residue) contain more contaminants and are more difficult to process (normalized temperatures are higher). Since the same feedstock and test conditions were used for all the catalysts disclosed in this application, the catalysts may be assessed directly using the normalized temperature.

[0034] The Table below compares the performance of the catalyst of this invention (Examples 1-4) with a commercial high-activity residuum catalyst (catalyst A). The catalyst performance for each catalyst is the average performance observed between 350-400 hours, a time period of generally slower deactivation, following the rapid initial deactivation of the catalyst. TABLE 4 Com- mercial Ex. 1 Ex. 2 Ex. 3 Ex. 4 Catalyst A Density, g/cc 1.0651 1.1487 1.1684 1.2275 1.4375 Normalized Temperature (° F.) for: Sulfur 751.8 735.0 733.7 730.1 736.4 Removal MCR 752.3 738.8 737.2 737.9 735.7 Removal Nitrogen 738.3 726.3 717.1 717.4 728.0 Removal Vanadium 716.4 707.9 721.4 728.8 730.2 Removal

[0035] The catalyst in Example 1 outperformed the commercial catalyst for vanadium removal, but it was less successful for the removal of sulfur, micro-carbon residue and nitrogen. The catalyst in Example 2 outperformed the commercial catalyst for vanadium removal but did not offer significant activity advantage for sulfur, micro-carbon residue and nitrogen removal. The catalyst in Example 3 outperformed the commercial catalyst for sulfur, nitrogen and vanadium removal, while performing at a normalized temperature within 2° F. of that of the commercial catalyst for micro-carbon residue removal. The catalyst of Example 4 offered additional sulfur removal activity relative to the catalyst from Example 3. This is a key advantage in most hydrotreating applications. This significant gain in sulfur removal activity over that of the commercial catalyst was achieved despite a significantly lower particle density and consequently lower dry weight of catalyst loaded into the test reactor, as shown in Table 4. 

What is claimed is:
 1. A method of making a hydrotreating catalyst which comprises the following steps: (a) mixing a refractory inorganic oxide carrier with an aqueous acidic solution comprising at least one component from Group VIII and at least one component from Group VIB to form particles of the catalyst; and (b) shaping, drying and calcining the particles of the catalyst.
 2. The method of claim 1, further comprising the following steps: (c) post-impregnating the particles of the catalyst with additional hydrogenation components including at least one component from Group VIII and at least one component from Group VIB; and (d) shaping, drying and calcining the particles of the catalyst.
 3. The method of claim 1, wherein the refractory inorganic oxide carrier of step (a) is mixed with at least one Group IVB component before the aqueous acidic solution is added.
 4. The method of claim 1, where in the mixture of step (a) is further treated with an acid selected from the group consisting of acetic acid, sulfuric acid, oxalic acid, hydrochloric acid, formic acid; nitric acid, phosphoric acid and citric acid.
 5. The method of claim 1, wherein the refractory inorganic oxide carrier is alumina.
 6. The method of claim 3, wherein the Group IVB component is selected from the group consisting of the metals and compounds of titanium, zirconium and hafnium.
 7. The method of claim 1, wherein the Group VIII metals are selected from the group consisting of the metals and compounds of nickel and cobalt.
 8. The method of claim 1, wherein the Group VIB metals are selected from the group consisting of the metals and compounds of molybdenum and tungsten.
 9. The method of claim 3, wherein the Group IVB metal is present in amounts ranging from 0.3 through 10 wt % of the catalyst.
 10. The method of claim 9, wherein the Group IVB metal is present in amounts ranging from 3 through 6 wt % of the catalyst.
 11. The method of claim 2, wherein the Group VIB component is present in amounts ranging from 5 through 25 wt % of the catalyst and Group VIII component is present in amounts ranging from 1 through 8 wt % of the catalyst.
 12. The method of claim 11, wherein the Group VIB component is present in amounts ranging from 10 through 20 wt % of the catalyst and Group VIII component is present in amounts ranging from 2 through 4 wt % of the catalyst.
 13. A catalyst prepared according to the method of claim 1, 2, 3 or
 4. 14. A catalyst composition comprising: (a) a refractory organic oxide carrier; (b) at least one component from Group VIII; (c) at least one component from Group VIB; and (d) at least one component from Group IVB.
 15. A method for the hydrotreating of a hydrocarbon feed containing a substantial amount of heteroatoms and other contaminants, which method comprises contacting said feed in a reaction zone under hydrotreating conditions comprising a temperature within the range of about 500° F. to about 850° F., a total pressure within the range of about 450 to about 3500 pounds per square inch gauge, a liquid hourly space velocity ranging from about 0.05 to about 5.0 hr.⁻¹, and a hydrogen partial pressure ranging from about 350 to about 3200 pounds per square inch gauge, in the presence of hydrogen and with a catalyst prepared by the method comprising: (a) mixing a refractory inorganic oxide carrier with an aqueous acidic solution comprising at least one component from Group VIII and at least one component from Group VIB to form particles of the catalyst; and (b) shaping, drying and calcining the particles of the catalyst.
 16. A method for the hydrotreating of a hydrocarbon feed containing a substantial amount of heteroatoms and other contaminants, which method comprises contacting said feed in a reaction zone under hydrotreating conditions comprising a temperature within the range of about 500° F. to about 850° F., a total pressure within the range of about 450 to about 3500 pounds per square inch gauge, a liquid hourly space velocity ranging from about 0.05 to about 5.0 hr.⁻¹, and a hydrogen partial pressure ranging from about 350 to about 3200 pounds per square inch gauge, in the presence of hydrogen and with a catalyst composition comprising: (a) a refractory organic oxide carrier; (b) at least one component from Group VIII; (c) at least one component from Group VIB; and (d) at least one component from Group IVB.
 17. The method of claim 15, wherein the refractory inorganic oxide carrier of step (a) is mixed with at least Group IVB component before the aqueous acidic solution is added.
 18. The method of claim 15, wherein the catalyst preparation further comprises: (c) post-impregnating the particles of the catalyst with additional hydrogenation components including at least one component from Group VIII and at least one component from Group VIB; and (d) shaping, drying and calcining the particles of the catalyst.
 19. The method of claim 15, wherein the mixture of step (a) is further treated with an acid selected from the group consisting of acetic acid, sulfuric acid, oxalic acid, hydrochloric acid, formic acid; nitric acid, phosphoric acid and citric acid.
 20. The method of claim 1, wherein the refractory inorganic oxide carrier has a pore volume falling within a range of 0.40-0.70 cc/g, a pore size distribution peak falling within a range of 50-110 angstroms, and less than 5% of said pore volume in pores having a pore diameter above 1000 angstroms. 